The snow ended at ~4PM, so I went out and turned on the heater. Nothing happened, and the IR image shows how much heat we lost. Will try re routing the cable for tighter coil spacing to see if I can get all of the heating tape on the two panels, and add some insulation to use it all for heating the surface instead of wasting it.
Will need to use some black tape or cloth duct tape over the foil covered wire to avoid seeing the cold snow reflected off the foil. aluminum is a great reflector for IR as are copper and gold.

Found this info:
Class 1 systems allow a layer of snow to accumulate during a heavy snowfall and then melt the snow over a several hour interval after the snowfall stops or slows down. These systems typically deliver 80 to 125 Btuh/sq ft (23 to 36 watts/sq ft) depending on the location.

looks like I need more concentrated heat.The Calorique panel they are sending is in the 50- 75 watts/sq ft range. I will use a variac to crank it up gradually.